Really Right Stuff B2-AS-II-M6 quick release clamp

The Really Right Stuff quick-release system is based on the Arca-Swiss standard and has two parts: a quick-release clamp and a quick-release plate. You always need both pieces of the system. The clamp will stay on your tripod head/accessory all the time, and the plate will stay on your camera all the time. You will need to purchase a separate quick-release plate for each camera or collared, telephoto lens that you want to mount in the quick-release clamp on your tripod head.
Clamp jaws open and close in one of two ways: by twisting a knurled knob on our tried & true screw-knob clamps; or by flipping a single lever on our innovative, patented lever-release clamps. The graceful Stainless Steel S-shaped cam-locking lever provides desirable benefits over traditional screw knob clamps.
This clamp has a NON-threaded center socket with countersink; mounting screw drops through from above into tapped female socket. This clamp cannot spin onto a threaded post. B2 AS II mounts on Really Right Stuff ballheads, current model Arca-Swiss ballheads*, and some Manfrotto heads.
*Some of the most recent Arca Swiss ballheads have clamps that cannot be removed by the consumer, such as the newest Z1.

Easy Top-Loading: In one quick action, the clamp can go from closed to fully open, allowing easy top-loading of Arca-Swiss-compatible quick-release camera and lens plates. No more lost shots while fumbling to feed the plates into the end of the clamp.

Visual Confirmation of Lock Position: You can readily observe if the lever is locked, half-open or fully open.

Low Profile: The lever does not protrude above or below the top or bottom of the clamp, and, in the closed position, the lever closely hugs the contours of the clamp. This makes it less of a "weed catcher" in the field and reduces the chance of being damaged in a fall.

Less Abrasive, No Twisting: The smooth contours of the lever are less abrasive than standard knurled knobs, and for those with arthritic hands, the graceful lever cams open and closed with just finger force.

Super Tough, Reliable: The Stainless Steel lever delivers a lifetime of wear and rides on a self-lubricating, wear-resistant bronze bearing surface. Delivers 50 lbs. of holding power under full compression (the fully closed position) with our plates. This is more than sufficient for any practical photographic application.